A type of boat structure which has evolved in recent times is a type called a pontoon boat. In a pontoon boat there are typically two individual pontoons which are held in a spaced apart relationship by a metal frame. The metal frame also provides a place for mounting a seat for one or more users to sit on. The pontoon boat may be propelled by paddle wheels on each side, by a small motor, or by oars that work in oarlocks mounted on the frame. Pontoon boats have been used successfully in whitewater, and also in still water for purposes of fishing.
One feature that exists in all pontoon boats is the frame that provides rigidity to the boat, and which holds the pontoons in a rigid position, and which provides the structure on which a seat may be placed. This frame also presents a problem in the use of pontoon boats. The frame is large, and typically attached to the pontoons in a way that is cumbersome and time consuming to remove of disassemble. The size and weight of the frame make it hard to put on the top of a car, and make it impossible to fit inside of a car. Even if the pontoons are deflated, the pontoons are spaced far enough apart to provide stability in the water, and this spacing makes the pontoons and the frame too wide and too bulky to fit inside a car. Instead of fitting the pontoon boat inside a car or even a pickup, the user is forced to haul the pontoon boat in a trailer. Having to hook up a trailer to haul the pontoon boat deprives the user of a certain amount of flexibility in transportation, and makes the use of the pontoon boat more troublesome.
A pontoon boat without a frame would provide certain advantages. If the pontoon boat were fully deflatable and did not have a rigid frame holding it together, it could fit into a trunk of a car, a station wagon, or a small pick-up.
The challenge for the pontoon boat without a frame is that it would be held together by a non-rigid and inflatable member. An inflatable member for performing this task would have to provide sufficient rigidity that the user could sit on the connecting member and be supported, and the pontoons would be held in a spaced apart relationship without excessive flexing or movement. This is difficult to achieve in an inflatable structure because unless the structure is inflated to a very high pressure, it would not have sufficient rigidity to replace the frame. A structure inflated to a high pressure has other disadvantages such as it is hard to inflate the structure to that pressure, and if a leak develops, it would quickly lose that pressure and become a boat with very bad characteristics.